Kelim, Chapter Eleven, Mishnah Four
1) If unclean iron was smelted together with clean iron and the greater part was from the unclean iron, [the vessel made of the mixture] is unclean;
a) If the greater part was from the clean iron, the vessel is clean.
b) If each was half, it is unclean.
2) The same law also applies to a mixture of cement and cattle dung.
3) A door bolt is susceptible to impurity, but [one of wood] that is only plated with metal is not susceptible to impurity.
4) The clutch and the crosspiece [of a lock] are susceptible to impurity.
5) A door-bolt:
a) Rabbi Joshua says: he may remove it from one door and hang it on another on Shabbat.
b) Rabbi Tarfon says: it is like all other vessels and may be carried about in a courtyard.
Section one: The unclean iron comes from vessels that were unclean, and the clean iron comes from vessels that are clean. The status of the new vessel follows the majority of the material used. If both materials are used in equal amounts the law is strict and the new vessel must be treated as unclean.
Section two: Cement is susceptible to impurity, whereas cattle dung is not. If one makes a vessel by mixing these two materials together, the vessel’s susceptibility to impurity depends on which material composes the majority, as in the previous section.
Section three: The susceptibility of the type of door belt referred to here depends upon whether it is made of metal, in which case it is susceptible, or of wood which is only plated with metal, in which case it is not susceptible.
Section four: These two pieces of the door are susceptible to impurity.
Section five: These laws relate to the door-bolt mentioned in section three. According to Rabbi Joshua one can remove it from one door and drag it to another door on Shabbat. But he can’t directly carry it, because it is not a vessel and one is not allowed to handle non-vessels on Shabbat. This opinion flows or at least accords with the opinion above, that the door bolt is not a vessel.
Rabbi Tarfon says that the door-bolt is a vessel and can be carried about in the courtyard, as can vessels in general on Shabbat. Since it is a vessel, it is also susceptible to impurity. Rabbi Tarfon disagrees with the opinion in section three.